Oil burner primary safety control



y 1951 A L. JUDSON 2,552,973

OIL BURNER PRIMARY SAFETY CONTROL Filed June 20, 1949' .SMOKE PI PECOMBUSTION CHAMBER (RE LAY 5AFETY TIMER RELAY BURNER (GNVUOH BURNERMOTOR THERMOSKTAT mufie/v TUF OR mow ALbE-RT L. JUDSOE Patented May 15,1951 OIL BURNER PRIMARY SAFETY CONTROL Albert L. Judson, Portland, reg.,assignor to Iron Fireman lllanufaoturingv fiompany, Portland, Oreg.

Application June 20, 1949, Serial N 0. 100,131

3 Cla ms.

ing motor and the ignition mechanism of such a burner.

Considered broadly, the present invention has for its purpose theprovision of an oil burner primary control having a simple and easilyunderstood circuit scheme and yet which will be reliable in operationand include the several desirable safety features which such a controlshould have.

It is a further purpose of this invention to provide a control schemeand mechanism which is complete with all required safety features andincludes the feature of intermittent ignition well known in the art.

A further purpose is to provide such a scheme and mechanism which can besimplified by leaving out the ignition circuit and connecting theignition transformer in parallel with the burner motor withouteliminating any of the safety features of the control.

Still a further purpose is to provide such a scheme and mechanism whichcan be further simplified by the elimination of the transformer and itslow voltage control circuit, and by placing the operating coil of therelay in the place normally held in the scheme by the primary winding ofthe transformer. be seen that this will result in a line voltage controlmuch more compact and more economical to build than anything shown inthe prior art and yet which will continue to include all the essentialoperational and safety features possessed by the more complete control.In the simplified control the line voltage limit control positioned asshown in the figure becomes the operating control or pilot instrument.

How my improved oil burner primary control is arranged and theadvantages thereof will be apparent from the following descriptionreferring to the attached drawing in which the single Figure 1 is aconventionalized diagram showing the mechanisms of the control.positioned in the circuits thereof.

Referring to the figure, there is shown a combustion chamber connectedby a smoke pipe to a chimney. For purposes of description it is assumedthat the combustion chamber is surrounded by a chamber through which iscirculated a heating medium such as air or water which is transported inthe usual way to a space to be heated. The thermostat is assumed to bein the space or medium Whose temperature is to be 0011? From the figureit will 2 trolled and the limit control is assumed to be so actuated asto be responsive to the temperature of the heating medium surroundingthe com-bustion chamber.

As shown in the figure, tension spring 62 through lever 46, adjustablefulcrum it i, and lever 59 biases temperature insensitive stern iltoward the smokepipe where it engages on the inner end of temperaturesensitive tube 40. As the temperature in the smokepipe increases, stem41 recedes into the smokepipe and the left end of lever 46 is moveddownward by spring E52. As the temperature in the srnckepipe decreases,tube 4%! con-tracts forcing stem 4| downward and the left end of lever46 upward against the bias of spring 62. l he relative movements of stemtl and lever 46 is adjustable by right or left movement of. fulcrum EIand is indicated by pointer 54 on scale 55. Held in lever 4e arefriction blocks 52 which frictionally engage stem 43 and cause stem 58to travel with lever 45 within the range of movement determined by theadjustable stop in the cooling direction and by the limit of throw ofresilient switch arm M8 in the heating direction. Resilient switch armI48 is biased toward the open position of contact pairs Il'2I31 and2l2-213. Switch arm IE8 and associated moving contacts I l2, W2, andstationary contacts I31, 213 form, therefore, a two circuit single throwswitch which is responsive to the increase or decrease of combustiontemperature through the above recited system of levers.

The safety timing switch has two bi-metal blades I49 and H2substantially parallel and similarly affected by ambient temperature.Additionally blade I I2 is affected by its associated electricresistance heater H5, when the circuit in Which the heater is connectedis energized. Resilient blade I48 carries insulating rigid bar I16, towhich it is riveted with silvered rivets. Bar I16 is secured with ahollow rivet to conducting resilient leaf spring I80. Leaf spring we issecured with silvered rivets to stiff conducting bridge I18. A dependingtongue on bi-metal blade I49 inserts through slots in bar Ilt, leaf Iand bridge I18 and bears laterally on bridge I18 to compensate for theeffect of ambient temperature on blade H2 and therefore to maintain theproper relation of the right end of bridge I18 with the lower end ofblade II2 with which it is normally engaged. When electric currentpasses through resistance heater I I5 for a predetermined time, bi-metalblade II2 warps to the right and slides off the end of bridge I18 whichis biased upward by both support I48 and leaf I80.

When i this occurs the circuit from blade I 48 to blade I I2 isinterrupted both at the junction of bridge I18 and blade H2 and by theseparation of the rivet heads at the left end of bridge I18 from therivet heads at the lower end of blade I48. To reset the switch it isnecessary to allow blade I I2 to cool and then manually to press theright end of bridge I18 downward until blade I I2 can spring back intoplace over the right end of bridge I18.

The relay switch comprises three stationary contacts I34, I45, and I40and three moving contacts 84, 96 and 90 carried respectively onresilient switch blades 83, 95 and89. The relay operator comprises frameI84, coil I85, armature I86 hinged to frame I84 and toggle compressionspring I94 biasing armature I86 to open position as shown. Operatinglever I26 linked to armature I86 by adjustable stop screw I3I andarcuate spring I98 allows the switch contacts to close when coil I85 isenergized and opens the switch contacts due to the action of Spring I94overcoming the bias of blades 83, 95, and 89 when the coil isole-energized.

The timing relay comprises resilient bi-metal blade I60 carrying movingcontacts I66 and I61 and normally biased to close moving contacts I66and I61 on stationary contacts I56a and I61a respectively. Associatedwith blade I60 is electric resistance heater 260 which, when energized,heats blade I60, causing it to warp upwardly and open switch contactpairs I66I68a and I61- In tracing the circuits of this control it iswell to remember that the electric service line is connected toterminals IOI and I02. Terminal IOI is usually considered the hotterminal and I02 the ground terminal. The limit control or other highvoltage pilot instrument if used is usually connected into the hot wireleading up to terminal IOI. Inside the instrument of the presentinvention it is simplest to trace the circuits starting from terminalIOI and proceeding to terminal I02. The circuits included in thecomplete control are:

A first circuit including wire I42, wire I39,

contacts I40, 90, relay switch blade 89, wire 85,

terminal I03, and the burner motor having its other terminal connectedto terminal I02.

A second circuit including wire I42, bi-metal blade I69, contacts I66,I66a, wire 265, blade I48, bridge I18, blade II2, heater II5, wire H1,200 and the primary winding of transformer 14 Whose other terminal isconnected to terminal I02 by wire I99.

A third circuit which includes wire I42, bimetal blade I48, contactsI12, I31, wire I32, relay switch contacts I34, 84 and blade 83 connectedto wires II1 and 200. ,7

A fourth circuit including wire I42, bi-metal blade I48 contacts 212,213, wire 26I, and heater 260 whose other terminal is connected toterminal I02 by wire 262. 7

A fifth circuit which is a low voltage control circuit complete initself and which includes the secondary winding of transformer 14, wire202, relay coil I85, wire 203, terminalI to which is connected athermostat or other pilot instrument, terminal I06, and wire 20I backtothe other side of the transformer secondary.

A sixth circuit which includes wire I42, bimetal blade I60, contactsI61, I61a, wire I44, contacts I45, 96, blade 95, wire 9|, and terminalI04 between which and terminal I02 isconnected the ignition transformerof the oil burner control system.

From the drawing it is evident that the control can be simplified byeliminating the sixth circuit and connecting the burner ignitionapparatus in parallel with the burner motor between terminal I03 andI02.

Also from the drawing it is evident that the control can be furthersimplified by eliminating the transformer and the fifth circuit andconnecting the relay coil I in the place in the second circuit shown forthe primary of the transformer. In this case the limit control wouldbecome the pilot instrument or, if desired, a line voltage thermostat oradditional pilot instrument can be connected in the service line leadingup to terminal IOI.

As shown schematically in the drawing the oil burner is not in operationsince the thermostat is satisfied and open. Assume then that thethermostat cools off and closes, thus indicating a need for thegeneration of additional heat. The primary transformer 14 is energizedfrom lines IOI and I02 through the timing relay contacts I66, I66a andthrough the safety timer. When the thermostat closes relay coil I85 isenergized from the secondary coil of transformer 14 and the secondaryload reflected in the primary circuit starts resistor II5 of the safetytimer to heat up. Also armature I 86 is attracted by coil I85 and rockslever I26 and allows relay blades 83, 95, 89 to close their respectivepairs of relay contacts. The burner motor is energized from lines IOIand I02 through relay contacts 90, I40. The burner ignition system isenergized from lines IOI, I02 through timing relay contacts I61, I510,and relay contacts 95, 96. Supposedly then the burner is in operationand hot products of combustion are being formed in the combustionchamber and beginning to find their way through the smoke pipe to thechimney and heating heat sensitive sleeve 40 on the way. As sleeve 40heats it expands inwardly of the smoke pipe taking with it heatinsensitive rod II which through the system of levers shown allowsspring 62 to pull the left end of lever 40 down taking with it stem 48engaged by friction blocks 52. Stem 48 pressing on lever I48 closesstack element contacts I12, I31 and 212, 213. As seen from the drawingthe closing of contacts I12, I31 completes a second circuit from linesIOI, I02 through the primary of transformer 14 via relay contacts 84,I34 and therefore makes the safety timer ineffective to open the primarycircuit. The closing of contacts 212, 213 energizes timing relayresistor 260 from lines IOI, I 02 which after a short delay heatsbimetal I60 sufliciently to open contacts I66, I66a and I61, I61athereby deenergizing the ignition system, taking the safety timer out ofcircuit and leaving the burner in normal operation.

Now assume that during this ignition period no ignition occurred or forany reason element 48 was not heated by the products of combustion. Thenspring 62 could not have closed I12, I31 and 212, 213. The timing relaywould not have operated, the ignition system would continue to operateand the resistor II5 of the safety timer would heat bimetal I I2 untilit moved away from bridge I18 and thus allowed the safety timer to breakthe transformer primary circuit and completely deenergize the control,shutting down the burner. In this case bridge I18 of the safety timerwould have to be reset in position on the end of blade II2 after bladeII2- had cooled sufiiciently to return it to a resettable position.Similarly if at any time when the burner is in normal operation, shouldthe element 40 drop in temperature, thus indicating a combustiondifficulty or fiame failure the contraction of element 4!! would forcelever 46 to overcome the bias of spring 62 and raise stem 48 allowingcontacts I12, I31 to open and deenergize the primary of transformer M.In this case however the control could start a new starting cycle of itsown accord as soon as timing relay blade 160 had cooled sufliciently toclose contacts I56, "36a and again energize the primary of transformer14 through the safety timer. Normal shutdown would, of course, be by theopening of the thermostat which would return the control circuits to thecondition shown in the drawing.

It should be noted that by a pre-determination of the resistance of thetiming relay heater 260 and its thermal location with respect to thebi-metal blade I60 of the timing relay a desirable adjustment of thedelay in the operation of the timing relay with respect to the operationof the combustion responsive switch is made Possible.

Having thus described the mechanism, circuits, and use of the presentinvention with respect to the prior art, I claim:

1. In a control system for an oil burner, a first circuit including afirst pair of relay switch contacts and a burner motor, a second circuitincluding a first pair of timing relay contacts, a normally closedsafety timing switch having an electrically energizeable actuator, andthe primary coil of a transformer, a third circuit in cluding a firstpair of combustion responsive switch contacts and a second pair of relayswitch contacts, a fourth circuit including a second pair of combustionresponsive switch contacts and an actuator for said timing relay, afifth circuit including the secondary coil of said transformer, anactuator for said relay, and condition responsive means for closing saidfifth circuit to energize said relay actuator, a sixth circuit includinga second pair of timing relay contacts, a third pair of relay switchcontacts, and ignition means for said burner, said first, second,fourth, and sixth circuits being connected in parallel across a sourceof electric power, said third circuit being connected in parallel withthat part of said second circuit which includes said first pair oftiming relay contacts and said safety timing switch, means for closingsaid relay contacts when said relay actuator is energized and foropening said relay contacts when said relay actuator is de-energized,means for opening said timing relay contacts when said timing relayactuator is energized and for closing said timing relay contacts whensaid timing relay actuator is de-energized, and means responsive to anincrease in combustion temperature to close said combustion responsiveswitch contacts and responsive to a decrease in combustion temperatureto open said combustion responsive switch contacts.

2. In a control system for an oil burner, a first circuit includin afirst pair of relay switch contacts and a burner motor, a second circuitincluding a pair of timing relay contacts, a normal- 1y closed safetytiming switch, having an electrically energizable actuator and theprimary coil of a transformer, a third circuit including a first pair ofcombustion responsive switch contacts and a second pair of relay switchcontacts, a fourth circuit including a second pair of combustionresponsive switch contacts and an actuator for said timing relay, afifth circuit including the secondary coil of said transformer, anactuator for said relay, and condition responsive means for closing saidfifth circuit to energize said relay actuator, said first, second andfourth circuits being connected in parallel across a source of electricpower, said third circuit being connected in parallel with that part ofsaid second circuit which includes said first pair of timing relaycontacts and said safety timing switch, means for closing said relaycontacts when said relay actuator is energized and for opening saidrelay contacts when said relay actuator is deenergized, means foropening said timing relay contacts when said timing relay actuator isenergized and for closing said timing relay contacts when said timingrelay actuator is de-energized, and means responsive to an increase incombustion temperature to close said combustion responsive switchcontacts and responsive to a decrease in combustion temperature to opensaid combustion responsive switch contacts.

3. In a control system for an oil burner, a first circuit including apair of timing relay contacts, a normally closed safety timing switchhaving an electrically energizeable actuator and means comprising aburner control device, a second circuit including a first pair ofcombustion responsive switch contacts, a third circuit including asecond pair of combustion responsive switch contacts and an actuator forsaid timing relay, said first and third circuits being connected inparallel across a source of electric power, said second circuit beingconnected in parallel with that part of said first circuit whichincludes said pair of timing relay contacts and said safety timingswitch, means for opening said timing relay contacts when said timingrelay actuator is energized and for closing said timing relay contactswhen said timing relay actuator is de-energized, and means responsive toan increase in combustion temperature to close said combustionresponsive switch contacts and responsive to a decrease in combustiontemperature to open said combustion responsive switch contacts.

/ ALBERT L. JUDSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,910,721 Taylor May 23, 19331,991,185 Williams Feb. 12, 1935 2,021,407 Erickson Nov. 19, 19352,022,188 Denison Nov. 26, 1935 2,117,021 Cotea May 10, 1938 2,195,649Hallenbeck Apr. 2, 1940 2,230,732 Tapp et a1. Feb. 4, 1941 2,486,612Pratt Nov. 1, 1949

